Replaced empty handle checks with MaybeHandles

src/objects.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 5843 matching lines @@
 
 template<class ContextObject>
 class JSObjectWalkVisitor {
  public:
   JSObjectWalkVisitor(ContextObject* site_context, bool copying,
                       JSObject::DeepCopyHints hints)
     : site_context_(site_context),
       copying_(copying),
       hints_(hints) {}
 
-  Handle<JSObject> StructureWalk(Handle<JSObject> object);
+  MUST_USE_RESULT MaybeHandle<JSObject> StructureWalk(Handle<JSObject> object);
 
  protected:
-  inline Handle<JSObject> VisitElementOrProperty(Handle<JSObject> object,
-                                                 Handle<JSObject> value) {
+  MUST_USE_RESULT inline MaybeHandle<JSObject> VisitElementOrProperty(
+      Handle<JSObject> object,
+      Handle<JSObject> value) {
     Handle<AllocationSite> current_site = site_context()->EnterNewScope();
-    Handle<JSObject> copy_of_value = StructureWalk(value);
+    MaybeHandle<JSObject> copy_of_value = StructureWalk(value);
     site_context()->ExitScope(current_site, value);
     return copy_of_value;
   }
 
   inline ContextObject* site_context() { return site_context_; }
   inline Isolate* isolate() { return site_context()->isolate(); }
 
   inline bool copying() const { return copying_; }
 
  private:
   ContextObject* site_context_;
   const bool copying_;
   const JSObject::DeepCopyHints hints_;
 };
 
 
 template <class ContextObject>
-Handle<JSObject> JSObjectWalkVisitor<ContextObject>::StructureWalk(
+MaybeHandle<JSObject> JSObjectWalkVisitor<ContextObject>::StructureWalk(
     Handle<JSObject> object) {
   Isolate* isolate = this->isolate();
   bool copying = this->copying();
   bool shallow = hints_ == JSObject::kObjectIsShallowArray;
 
   if (!shallow) {
     StackLimitCheck check(isolate);
 
     if (check.HasOverflowed()) {
       isolate->StackOverflow();
-      return Handle<JSObject>::null();
+      return MaybeHandle<JSObject>();
     }
   }
 
   if (object->map()->is_deprecated()) {
     JSObject::MigrateInstance(object);
   }
 
   Handle<JSObject> copy;
   if (copying) {
     Handle<AllocationSite> site_to_pass;
@@ skipping 20 matching lines @@
     // Deep copy local properties.
     if (copy->HasFastProperties()) {
       Handle<DescriptorArray> descriptors(copy->map()->instance_descriptors());
       int limit = copy->map()->NumberOfOwnDescriptors();
       for (int i = 0; i < limit; i++) {
         PropertyDetails details = descriptors->GetDetails(i);
         if (details.type() != FIELD) continue;
         int index = descriptors->GetFieldIndex(i);
         Handle<Object> value(object->RawFastPropertyAt(index), isolate);
         if (value->IsJSObject()) {
-          value = VisitElementOrProperty(copy, Handle<JSObject>::cast(value));
-          RETURN_IF_EMPTY_HANDLE_VALUE(isolate, value, Handle<JSObject>());
+          ASSIGN_RETURN_ON_EXCEPTION(
+              isolate, value,
+              VisitElementOrProperty(copy, Handle<JSObject>::cast(value)),
+              JSObject);
         } else {
           Representation representation = details.representation();
           value = Object::NewStorageFor(isolate, value, representation);
         }
         if (copying) {
           copy->FastPropertyAtPut(index, *value);
         }
       }
     } else {
       Handle<FixedArray> names =
           isolate->factory()->NewFixedArray(copy->NumberOfLocalProperties());
       copy->GetLocalPropertyNames(*names, 0);
       for (int i = 0; i < names->length(); i++) {
         ASSERT(names->get(i)->IsString());
         Handle<String> key_string(String::cast(names->get(i)));
         PropertyAttributes attributes =
             JSReceiver::GetLocalPropertyAttribute(copy, key_string);
         // Only deep copy fields from the object literal expression.
         // In particular, don't try to copy the length attribute of
         // an array.
         if (attributes != NONE) continue;
         Handle<Object> value =
             Object::GetProperty(copy, key_string).ToHandleChecked();
         if (value->IsJSObject()) {
-          Handle<JSObject> result = VisitElementOrProperty(
-              copy, Handle<JSObject>::cast(value));
-          RETURN_IF_EMPTY_HANDLE_VALUE(isolate, result, Handle<JSObject>());
+          Handle<JSObject> result;
+          ASSIGN_RETURN_ON_EXCEPTION(
+              isolate, result,
+              VisitElementOrProperty(copy, Handle<JSObject>::cast(value)),
+              JSObject);
           if (copying) {
             // Creating object copy for literals. No strict mode needed.
             JSObject::SetProperty(
                 copy, key_string, result, NONE, SLOPPY).Assert();
           }
         }
       }
     }
 
     // Deep copy local elements.
@@ skipping 11 matching lines @@
             ASSERT(!elements->get(i)->IsJSObject());
           }
 #endif
         } else {
           for (int i = 0; i < elements->length(); i++) {
             Handle<Object> value(elements->get(i), isolate);
             ASSERT(value->IsSmi() ||
                    value->IsTheHole() ||
                    (IsFastObjectElementsKind(copy->GetElementsKind())));
             if (value->IsJSObject()) {
-              Handle<JSObject> result = VisitElementOrProperty(
-                  copy, Handle<JSObject>::cast(value));
-              RETURN_IF_EMPTY_HANDLE_VALUE(isolate, result, Handle<JSObject>());
+              Handle<JSObject> result;
+              ASSIGN_RETURN_ON_EXCEPTION(
+                  isolate, result,
+                  VisitElementOrProperty(copy, Handle<JSObject>::cast(value)),
+                  JSObject);
               if (copying) {
                 elements->set(i, *result);
               }
             }
           }
         }
         break;
       }
       case DICTIONARY_ELEMENTS: {
         Handle<SeededNumberDictionary> element_dictionary(
             copy->element_dictionary());
         int capacity = element_dictionary->Capacity();
         for (int i = 0; i < capacity; i++) {
           Object* k = element_dictionary->KeyAt(i);
           if (element_dictionary->IsKey(k)) {
             Handle<Object> value(element_dictionary->ValueAt(i), isolate);
             if (value->IsJSObject()) {
-              Handle<JSObject> result = VisitElementOrProperty(
-                  copy, Handle<JSObject>::cast(value));
-              RETURN_IF_EMPTY_HANDLE_VALUE(isolate, result, Handle<JSObject>());
+              Handle<JSObject> result;
+              ASSIGN_RETURN_ON_EXCEPTION(
+                  isolate, result,
+                  VisitElementOrProperty(copy, Handle<JSObject>::cast(value)),
+                  JSObject);
               if (copying) {
                 element_dictionary->ValueAtPut(i, *result);
               }
             }
           }
         }
         break;
       }
       case SLOPPY_ARGUMENTS_ELEMENTS:
         UNIMPLEMENTED();
@@ skipping 11 matching lines @@
       case FAST_HOLEY_DOUBLE_ELEMENTS:
         // No contained objects, nothing to do.
         break;
     }
   }
 
   return copy;
 }
 
 
-Handle<JSObject> JSObject::DeepWalk(
+MaybeHandle<JSObject> JSObject::DeepWalk(
     Handle<JSObject> object,
     AllocationSiteCreationContext* site_context) {
   JSObjectWalkVisitor<AllocationSiteCreationContext> v(site_context, false,
                                                        kNoHints);
-  Handle<JSObject> result = v.StructureWalk(object);
-  ASSERT(result.is_null() || result.is_identical_to(object));
+  MaybeHandle<JSObject> result = v.StructureWalk(object);
+  Handle<JSObject> for_assert;
+  ASSERT(!result.ToHandle(&for_assert) || for_assert.is_identical_to(object));
   return result;
 }
 
 
-Handle<JSObject> JSObject::DeepCopy(Handle<JSObject> object,
-                                    AllocationSiteUsageContext* site_context,
-                                    DeepCopyHints hints) {
+MaybeHandle<JSObject> JSObject::DeepCopy(
+    Handle<JSObject> object,
+    AllocationSiteUsageContext* site_context,
+    DeepCopyHints hints) {
   JSObjectWalkVisitor<AllocationSiteUsageContext> v(site_context, true, hints);
-  Handle<JSObject> copy = v.StructureWalk(object);
-  ASSERT(!copy.is_identical_to(object));
+  MaybeHandle<JSObject> copy = v.StructureWalk(object);
+  Handle<JSObject> for_assert;
+  ASSERT(!copy.ToHandle(&for_assert) || !for_assert.is_identical_to(object));
   return copy;
 }
 
 
 Handle<Object> JSObject::GetDataProperty(Handle<JSObject> object,
                                          Handle<Name> key) {
   Isolate* isolate = object->GetIsolate();
   LookupResult lookup(isolate);
   {
     DisallowHeapAllocation no_allocation;
@@ skipping 6309 matching lines @@
   Handle<Map> new_map = GetPrototypeTransition(map, prototype);
   if (new_map.is_null()) {
     new_map = Copy(map);
     PutPrototypeTransition(map, prototype, new_map);
     new_map->set_prototype(*prototype);
   }
   return new_map;
 }
 
 
-Handle<Object> JSObject::SetPrototype(Handle<JSObject> object,
-                                      Handle<Object> value,
-                                      bool skip_hidden_prototypes) {
+MaybeHandle<Object> JSObject::SetPrototype(Handle<JSObject> object,
+                                           Handle<Object> value,
+                                           bool skip_hidden_prototypes) {
 #ifdef DEBUG
   int size = object->Size();
 #endif
 
   Isolate* isolate = object->GetIsolate();
   Heap* heap = isolate->heap();
   // Silently ignore the change if value is not a JSObject or null.
   // SpiderMonkey behaves this way.
   if (!value->IsJSReceiver() && !value->IsNull()) return value;
 
   // From 8.6.2 Object Internal Methods
   // ...
   // In addition, if [[Extensible]] is false the value of the [[Class]] and
   // [[Prototype]] internal properties of the object may not be modified.
   // ...
   // Implementation specific extensions that modify [[Class]], [[Prototype]]
   // or [[Extensible]] must not violate the invariants defined in the preceding
   // paragraph.
   if (!object->map()->is_extensible()) {
     Handle<Object> args[] = { object };
     Handle<Object> error = isolate->factory()->NewTypeError(
         "non_extensible_proto", HandleVector(args, ARRAY_SIZE(args)));
-    isolate->Throw(*error);
-    return Handle<Object>();
+    return isolate->Throw<Object>(error);
   }
 
   // Before we can set the prototype we need to be sure
   // prototype cycles are prevented.
   // It is sufficient to validate that the receiver is not in the new prototype
   // chain.
   for (Object* pt = *value;
        pt != heap->null_value();
        pt = pt->GetPrototype(isolate)) {
     if (JSReceiver::cast(pt) == *object) {
       // Cycle detected.
       Handle<Object> error = isolate->factory()->NewError(
           "cyclic_proto", HandleVector<Object>(NULL, 0));
-      isolate->Throw(*error);
-      return Handle<Object>();
+      return isolate->Throw<Object>(error);
     }
   }
 
   bool dictionary_elements_in_chain =
       object->map()->DictionaryElementsInPrototypeChainOnly();
   Handle<JSObject> real_receiver = object;
 
   if (skip_hidden_prototypes) {
     // Find the first object in the chain whose prototype object is not
     // hidden and set the new prototype on that object.
@@ skipping 4665 matching lines @@
 #define ERROR_MESSAGES_TEXTS(C, T) T,
   static const char* error_messages_[] = {
       ERROR_MESSAGES_LIST(ERROR_MESSAGES_TEXTS)
   };
 #undef ERROR_MESSAGES_TEXTS
   return error_messages_[reason];
 }
 
 
 } }  // namespace v8::internal